1. Field of the Invention
The present invention relates to an antitumor agent, in particular, a novel antitumor agent containing as the effective ingredient a cyanine dye.
2. Description of the Prior Art
Generally, antitumor agents can be briefly grouped into antibiotic and immunological types. Since both types of antitumor agents do not distinguish between tumor and normal cells, they are strongly toxic to normal cells and unpromising in the conquest of malignant tumors.
Recently highlighted is "Biological Response Modifier (abbreviated as "BRM" hereinafter)", a substance regulating the response in living body and useful in the treatment of malignant tumors in vivo. Most of the BRMs which are in earnest investigation are proteinaceous substances from animal as is the case, for example, of interferon, tumor necrosis factor, lymphotoxin and interleukin. Such proteinaceous BRMs have the disadvantage that their large-scale preparation in high-purity and pyrogen-free form is very difficult because they are usually produced in a culture of hemopoietic cells or micro-organisms wherein the BRM production gene has been introduced by the gene recombinant technique, as well as the advantage that they cause less toxicity and side effect because they are inherently produced in vivo.
Furthermore, most of the proteinaceous BRMs exhibit no antitumor activity when orally administered. Thus, any BRM antitumor agent which is efficacious through oral administration has been highly sought after.